Just the Concepts of Electrical Engineering You Need #

Don’t tell the college admissions officials I blatantly lied to here but an advanced knowledge of electrical engineering is not generally required to create an FRC electrical board.

That’s not to say that understanding electricity will not help you, and a basic knowledge of Direct voltage and current (DC) will be required. That is what this section will attempt to teach- an understanding of what is actually happening in the wires when you plug them in.

What voltage, current, and resistance actually do #

Let’s get right into it with current. When electricity flows through a wire, charges can be imagined to move in the wire like water in a pipe.

Get used to the pipe metaphor, electrical engineers love it

Unlike water, however, electrical charges flow at nearly the speed of light through the wire.

Current #

Current measures the number of charges passing through a point in the wire per second. Current is measured in amperes, but everyone calls them amps because it sounds cooler. It essentially measures how ‘much’ electricity is flowing through a wire, like measuring the volume of water flowing through a pipe per second.

So to recap, we plug a battery’s + and - terminals into a circuit and current flows from the battery’s + terminal to the battery’s - terminal.

If you (Landon) have taken a basic physics class and are about to enlighten us all with the ingenious statement that ‘actually, current flows from the more negative terminal to the more positive terminal’, I invite you to shut the fuck up (Landon) and accept that nobody uses the electron flow model.

But what determines how much current actually flows through a simple circuit, like a light connected to a battery? That requires the help of two other measurements.

Voltage #

Officially, voltage is a measure of the electrical ‘potential difference’ between two points. Imagine voltage as a measurement of the force that pushes current through a wire. If the voltage is higher, more current is shoved through the wire than if the voltage is lower. Voltage is measured in ‘volts’.

It is very important to remember that voltage is a measurement between two points. For example, a 12 volt battery has a positive and negative terminal: we would say that there is 12 volts across the terminals.

If electrical current can be thought of as how much water flows through a pipe per second, then voltage can be thought of as water pressure. If the pressure is higher, more water will flow through the same sized pipe. That leads us to the final measure needed to model basic circuits: resistance.

Resistance #

Think of resistance as how much something pushes back, or ‘resists’ the flow of electrical current. Resistance is measured in ‘ohms’, or the greek character ‘Ω’, a decision made by the scriptwriters foreshadowing what you will learn later.

To help, let’s go back to the water in a pipe model. If voltage is the water pressure, and current is the amount of water passing through the pipe per second, then resistance is the size of the pipe that the water is going through.

Resistance explained by a water pipe

An important difference between the water-in-a-pipe model and real electricity is that water changes speed when its flow is impeded, but charges almost always travel at near the speed of light. Remember that electrical resistance will reduce the number of charges that can pass at a given voltage, but it does not slow the charges down.

Here’s another depiction of what resistance does, but with little peanut-shaped gremlins being forcefully pushed into a body bag.

Resistance explained but worse

Open for an explanation of the ‘Gremlin Model’ of current flow

The current gremlin’s ribcage cracks as he wails in agony.
resistance is deaf to the screams– it’s not in his department to care. His assigned task is just to pull the rope.
Likewise, voltage has one quest; one purpose; one ambition; he must push current through the bag.
No matter the cost.

Who must accept responsibility for the fate of the current gremlin?

Is `voltage` responsible? #

It just pushes current.
It doesn’t tighten the rope.
It wouldn’t hurt a fly.
It just needs current to get through.

Is `resistance` responsible? #

It pulls the rope.
It doesn’t wonder what the rope does.
It’s not their job to wonder.
It just pulls the rope

Do with this information what you must.

The Formalities #

Hopefully, you have a grasp of what voltage, current, and resistance actually are. You’ll learn how these measurements are used throughout the rest of the book.

So, voltage pushes current through a wire, which has resistance that limits how much current can be pushed by voltage. But how do we calculate, for example, how much current will flow through a wire when 12 volts are applied across it?

Ohm’s law triangle: V is on top, with I and R side-by-side on the bottom

For this, we use Ohm’s Law.

\( V = I * R \)

\( I = \frac{V}{R} \)

\( R = \frac{V}{I} \)

We will later learn that Ohm’s Law is not actually a law. There are a lot of phenomena that break it, notably most semiconductors and static electricity. Despite this, ohm’s law holds true for every case we will use it for in the book.

Ohm’s law relates voltage (V), current (I), and resistance (R).